Two die when faulty muffler leaks carbon monoxide into cockpit

These March 2004 Accident Reports are provided by the National Transportation Safety Board. Published as an educational tool, they are intended to help pilots learn from the misfortunes of others.

Aircraft: Cessna 170.

Location: Herron, Wash.

Injuries: 2 Fatal.

Aircraft damage: Destroyed.

What reportedly happened: The plane, with two men on board, was on a local cross-country flight in VFR conditions over Puget Sound. According to the last nine minutes of radar data, the airplane descended from 3,400 to 300 feet then disappeared from radar coverage. There was no distress call. Sixteen days after it was reported missing, Search and Rescue personnel located the airplane in a water inlet at a depth of 132 feet. The plane was recovered with the pilot and the passenger still inside. The post-accident examination of the engine and airframe revealed multiple cracks in the muffler as a result of undetected oxidation and normal thermal degradation. This allowed exhaust gases direct access to cabin air through the heater system. Toxicological testing of the pilot and passenger revealed carbon monoxide levels of 45% and 46%. Autopsies determined that both men were incapacitated by carbon monoxide and drowned when the plane hit the water.

Probable cause: The failure of the muffler, resulting in a carbon monoxide leak into the cabin, rendering the pilot incapacitated, and the subsequent uncontrolled descent and impact with water.

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Aircraft: Piper Cherokee.

Location: Alma, Ga.

Injuries: 3 Fatal.

Aircraft damage: Destroyed.

What reportedly happened: The private pilot, who had an instrument rating, had 5,500 hours. He was flying a cross-country flight under visual flight rules and requested a slow, gradual descent toward the airport. Air traffic control approved the request and instructed him to maintain VFR. The last recorded radar position for the flight was approximately nine nautical miles southeast of the airport at an altitude of 2,400 feet msl. The controller told the pilot, “radar contact lost, squawk VFR change to advisory frequency approved.” The pilot acknowledged the transmission and there was no more radio communication. Several hours later the wreckage was found in a wooded area less than a mile from the runway, approximately 1,100 feet to the left of a straight-in course for runway 33. An unbound Jeppesen approach plate dated Feb. 2, 2001, for the Alma VOR or GPS Runway 33 approach was found near the wreckage in a plastic sleeve. There was no record of the pilot asking for a clearance to execute the approach.

Probable cause: The in-flight decision to continue VFR procedures into IFR conditions and the failure to maintain control, which resulted in the subsequent collision with trees during approach.

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Aircraft: Cessna 152.

Location: West Jordan, Utah.

Injuries: None.

Aircraft damage: Substantial.

What reportedly happened: A student and instructor pilot were practicing ground reference maneuvers at an altitude of approximately 1,000 feet when the engine began to run rough. They attempted to trouble shoot the problem while simultaneously heading back to the airport.

The engine did not produce enough power for them to maintain level flight, then quit. The instructor took the controls and initiated a forced landing in a snow-covered field. During the landing, the nose landing gear caught the snow and the airplane nosed over. The post-crash examination of the engine revealed a hole in the No. 1 piston, and a fractured exhaust valve for the No. 1 cylinder.

Probable cause: The failure of the exhaust valve resulting in the exhaust valve/piston contact and the subsequent total loss of engine power.

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Aircraft: Cessna 182.

Location: Rozel, Kan.

Injuries: 1 Fatal.

Aircraft damage: Destroyed.

What reportedly happened: The pilot held a commercial certificate and had approximately 8,800 hours, most of that from low-level agricultural operations. He had flown 150 hours in the previous six months, but had less than 20 hours of flight experience in actual instrument conditions. A caller representing the accident airplane telephoned for a weather briefing prior to departure but did not specifically request and was not provided with a standard weather briefing. The information provided by the flight service station briefer indicated VFR conditions at the time the call was placed. The briefer did not provide available weather forecast and information that would have depicted instrument meteorological conditions en route and at the destination airport at the estimated time of the aircraft’s flight and arrival. The pilot departed on a cross-country flight at night in instrument meteorological conditions but did not file a flight plan. The purpose of the flight was to reposition the aircraft so that it could be used for an aerial survey. The plane’s owner told investigators that the pilot, who was renting the airplane, did not fly more than 1,000 feet above ground level most of the time and he had not flown by instruments for more than three years. Pilots in the area around the time of the accident reported the weather as 1,000-foot ceilings and visibility of four miles in haze.

When the pilot failed to arrive at the destination airport, family members called authorities. The aircraft wreckage was found in an agricultural field. Investigators determined it hit the ground nose first and under power. No pre-crash mechanical problems were found.

Probable cause: The inadvertent flight into instrument meteorological conditions, spatial disorientation and aircraft control not maintained by the pilot during cruise flight. Contributing to the accident were the night instrument meteorological conditions due to low ceilings and low visibility, an incomplete pre-flight weather briefing, and the lack of recent experience in instrument meteorological conditions.

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Aircraft: Piper Cherokee.

Location: Knox City, Texas.

Injuries: None.

Aircraft damage: Substantial.

What reportedly happened: During a cross-country flight, the 194-hour private pilot decided to land in a field at his ranch. Upon touch down, the left main landing tire sunk into the soft ground and pulled the aircraft to the left. The pilot tried to correct using right rudder but the wheel continued to sink and the left wing hit the ground. The nose gear folded up into the wheel well and then the right main landing gear collapsed. Both wings were substantially damaged from ground impact. The pilot told investigators that he did not realize the ground was that soft until the wheels got stuck.

Probable cause: The pilot’s attempt to land on terrain not suitable for landing.